Heat transfer method and apparatus

ABSTRACT

Desalination apparatus for boiling salt water and condensing the resulting steam having a primary heat transfer unit with a twisted and spirally formed heat transfer tubular conduit for the salt water which is rotated within a steam chamber for heating the salt water while maintaining the salt water in the rotating tubular conduit substantially in its liquid state by the pressure increase resulting from its rotation. Steam emanating from the salt water heated by the primary heat transfer unit is conducted through a condenser having elongated inner and outer coaxial twisted tubes and through which the inlet salt water is conducted, thereby preheating the cold water while condensing the steam. The hot salt water residue from the primary heat transfer unit is conducted through a secondary heat transfer unit (like the condenser in construction) for preheating the inlet salt water further before it is conducted to the primary heat transfer unit.

Uited States atent 2,311,984 2/1943 Guild lnventor Ralph D. CooksleyWestbrook, Conn.

Appl. No. 813,570

Filed Apr. 4, 1969 Patented Jan. 4, 1972 Assignee Thermaline CorporationWaterford, Conn.

HEAT TRANSFER METHOD AND APPARATUS 9 Claims, 2 Drawing Figs.

US. Cl 165/1, 165/86 Int. Cl F28d 11/00 Field of Search 165/111, 86, 89,1,92, 113

References Cited UNITED STATES PATENTS Primary Examiner-Charles SukaloAttorney-Prutzman, Hayes, Kalb & Chilton ABSTRACT: Desalinationapparatus for boiling salt water and condensing the resulting steamhaving a primary heat transfer unit with a twisted and spirally formedheat transfer tubular conduit for the salt water which is rotated withina steam chamber for heating the salt water while maintaining the saltwater in the rotating tubular conduit substantially in its liquid stateby the pressure increase resulting from its rotation. Steam emanatingfrom the salt water heated by the primary heat transfer unit isconducted through a condenser having elongated inner and outer coaxialtwisted tubes and through which the inlet salt water is conducted,thereby preheating the cold water while condensing the steam. The hotsalt water residue from the primary heat transfer unit is conductedthrough a secondary heat transfer unit (like the condenser inconstruction) for preheating the inlet salt water further before it isconducted to the primary heat transfer unit.

HEAT TRANSFER METHOD AND APPARATUS BRIEF SUMMARY OF THE INVENTION Thepresent invention relates to improved heat transfer method and apparatusfor transferring thermal energy between two fluids.

It is a principal object of the present invention to provide new andimproved heat transfer method and apparatus for transferring thermalenergy between fluids and which provide improved thermal conductivitybetween the fluids.

It is another object of the present invention to provide new andimproved transfer method and apparatus which provide improved heattransfer within the fluids and improved scrubbing or wiping action ofthe fluids on the thermal conductor therebetween.

It is a still further object of the present invention to provide new andimproved heat transfer method and apparatus for reducing the size andcost of equipment providing any desired rate of thermal energy transfer.

It is another object of the present invention to provide new andimproved heat transfer method and apparatus useful for efficientlytransferring thermal energy between gases (including both wet and drysteam), between liquids, or between a gas and a liquid.

It is a further object of the present invention to provide new andimproved heat transfer method and apparatus for transferring thermalenergy from or to a liquid which is approximately at its boiling pointwithout diminishing the thermal conductivity due to pockets of vaporizedliquid at the surface of the thermal conductor.

It is another object of the present invention to provide new andimproved heat transfer method and apparatus for the continuous transferof thermal energy between two fluids which provide for heat transfer tothe energy receiving fluid with such fluid at a pressure above its inletand outlet pressures.

It is another object of the present invention to provide new andimproved heat transfer method and apparatus for boiling a liquid. Forexample, the heat transfer method and apparatus of the present inventionhas special application in desalination through the process of boilingsalt water and condensing the resulting steam.

It is a further object of the present invention to provide new andimproved heat transfer method and apparatus with which the rate ofthermal transfer between two moving fluids is vastly improved by thedynamic forces of the moving fluids.

It is a still further object of the present invention to provide new andimproved heat transfer apparatus which is useful for transferringthermal energy in either direction between two fluids.

Other objects will be in part obvious and in part pointed out more indetail hereinafter.

A better understanding of the invention will be obtained from thefollowing detailed description and the accompanying drawings of anillustrative application of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a generally schematic illustration, partly broken away andpartly in section, of a heat transfer apparatus incorporating thepresent invention and employing the heat transfer method of the presentinvention; and

FIG. 2 is a longitudinal elevation section view, partly broken away andpartly in section, of a primary heat transfer unit of the heat transferapparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT Refen'ing now to the drawings indetail wherein like numerals represent like parts, an embodiment of aheat transfer apparatus 8 incorporating the present invention andemploying the heat transfer method of the present invention is shownbeing applied for converting salt water to fresh water through theprocess of boiling the salt water and condensing the resulting steam. Aninlet pipe 10 of the apparatus provides for conducting inlet salt waterfrom a suitable pump (not shown) to a condenser 12 where the inlet saltwater is employed for condensing steam (generated as describedhereinafter) conducted to the condenser via a steam inlet pipe 14 anddischarged from the condenser as pure fresh water via an outlet pipe 16,it being understood that the condenser 12 functions to preheat the inletsalt water while condensing the steam.

The inlet salt water is preheated further by a secondary heat exchanger22 having a salt water inlet pipe 24 and a salt water outlet pipe 26connected to an inlet pipe 28 of a primary heat exchanger 30. Hot saltwater residue or concentrate (hereinafter more fully explained) isconducted to the secondary heat exchanger 22 via an inlet pipe 32 forheating the salt water and is discharged from the heat transferapparatus 8 via an outlet pipe 34.

Steam is admitted to the primary heat exchanger 30 via an inlet pipe 40and is discharged from the primary heat exchanger 30 via an outlet 42and preferably after the steam is condensed, in which case the primaryheat exchanger 30 could also be employed as the primary condenser forcondensing the steam of a separate closed system, for example a systemin which the steam is used to drive a turbine or other power equipment.

The heat exchanger 30 comprises a stationary housing with a pair ofcoaxial circular end plates 44, 46, outer and inner coaxial cylindricalcasings 48, 50 received within opposed circular recesses in the endplates, and tension rods 52 connecting the end plates. An annular waterjacket formed between the coaxial cylinder casings 48, 50 provides forpreheating the inlet salt water further, the inlet salt water beingconducted through the jacket from the jacket inlet pipe 28 to the jacketoutlet pipe 56.

The jacket outlet pipe 56 is connected via a suitable coupling 58 to anaxial inlet passage 60 in one end of a shaft 62 rotatably mounted on theend plates 44, 46. The shaft 62 has an axial outlet passage 64 at itsopposite end which is connected to a separator inlet pipe 66 via asuitable coupling 70, and a primary heat transfer conduit 72 having apair of axially spaced connectors 74, 76 and a spiral tube 78 betweenthe connectors 74, 76 provides a fluid connection between the inlet andoutlet passages 60, 64.

Accordingly the steam conducted to the heat transfer chamber 79 withinthe inner casing 50 provides for heating the salt water passing throughthe primary heat transfer conduit 72, preferably so that a substantialpercentage of the salt water will be converted to steam which is thenseparated from the remaining hot salt water concentrate or residue inthe gravity separator 66, the steam being conducted from the separator66 to the condenser 12 via a separator outlet pipe 80 and the salt waterresidue being conducted from the separator to the secondary heatexchanger 22 via a separator outlet pipe 82. Also, an auxiliary saltwater inlet pipe 84 is provided for flushing the hot salt water residuethrough the secondary heat exchanger 22 where such is desirable, forwhich purpose a manual valve 86 is provided for selectively flushing theheat exchanger 22 and a one-way check valve 88 is provided forpreventing backflow to the separator 66 when the valve 86 is open.

The shaft 62 and primary heat transfer conduit 72 form a rigid unitwhich is rotated by a suitable motor 90 through a chain and sprocketdrive arrangement 92 interconnecting the shaft 62 and motor shaft 94.The salt water pressure in the tube 78 is thereby increased by thecentrifugal force caused by the tube rotation. In addition the spiraltube 78 is formed, as by pretwisting the tube, with a plurality ofhelical convolutions providing alternate grooves and ridges within (andwithout) the tube which cause the salt water to travel helically aroundthe inside surface of the tube 78 as it is conducted through the tubefrom the inlet passage 60 to the outlet passage 64, and the centrifugalforce caused by such helical motion of the salt water produces anadditional increase in the salt water pressure.

Preferably the salt water pressure increase from such centrifugal forcesis sufficient to keep preferably at least a substantial portion of thesalt water within the tube in its liquid state and preferably enoughliquid to cover the entire inside irregular surface of the tube, so asto substantially reduce if not completely eliminate the formation ofsteam pocket on the inside surface of the tube and to thereby maintain ahigh rate of thermal conductivity. in addition the helical flow of thesalt water within the tube will increase the scrubbing action on theinside surface of the tube 78 and turbulence within the tube which willincrease the rate of heat transfer within the salt water throughconvection. Although as indicated it is preferred that at least asubstantial portion of the salt water remains in the liquid state as itpasses through the tube 78, the salt water will boil rapidly once itreaches the outlet passage 64, and the steam so formed will separate inthe gravity separator 66 from the remaining residue or concentrate whichis conducted to the secondary heat exchanger 22 to assist in preheatingthe inlet salt water.

Also, as previously indicated, it may be useful to use the heatexchanger 30 as a steam condenser for a separate steam system. in suchinstance, or in any case where condensation is present in the steamchamber 79, the condensation will form on the outer surface of theprimary heat transfer tube 78. However, the spinning tube 78 will throwoff such water particles and thereby maintain the high rate of heattransfer through the wall of the tube 78. In addition the spinning tube78 will cause a scrubbing action on the external surface of the tube 78and turbulence within the steam chamber 79, thereby increasing the rateof heat transfer through the wall of the tube 78 and increase the rateof heat transfer within the steam chamber through convection.

The condenser 12 and secondary heat exchanger 22 are similarlyconstructed with an elongated conduit 96 providing, in the condenser,for conducting the inlet salt water through the condenser, and in thesecondary heat exchanger, for conducting the hot salt water residuethrough the exchanger. inner and outer elongated twisted tubes 98, 100respectively, are coaxially mounted within the conduit 96 to form agenerally spiral intermediate passageway 102 for conducting the steamthrough the condenser 12 and the inlet salt water through the heatexchanger 22. The spiral fluid flow through the passageway 102 andaround the inner and outer walls of the inner and outer tubesrespectively, provides for increasing the scrubbing action on the wallsof the twisted tubes and rate of thermal conductivity through the walls.In addition such spiral motion of the fluid provides for increasing theheat transfer within the fluids by convection.

it can be seen therefore that the method and apparatus of the presentinvention provide economical and efficient heat transfer means havingutility in the desalination of water and, more generally, utility inheating a liquid to its boiling point with steam while maintaining ahigh rate thermal conductivity between the liquid and steam.

As will be apparent to persons skilled in the art, variousmodifications, adaptations and variations of the foregoing specificdisclosure can be made without departing from the teachings of thepresent invention.

I claim:

1. A method of transferring thermal energy from steam to a second fluidcomprising the steps of providing a fluid conduit for the second fluidhaving an outer heat transfer wall separating the second fluid from thesteam, rotating the fluid conduit in the steam to increase the scrubbingaction of the steam on the heat transfer wall and to reduce theformation of steam condensation on the heat transfer wall due to thecombined effect of the scrubbing action and the centrifugal forceproduced by the rotating fluid conduit, and conducting the second fluidthrough the rotating fluid conduit.

2. The method of claim 1 wherein the second fluid is conducted throughthe rotating conduit with its highest temperature sufficiently low toprovide that the second fluid remains substantiall in its liquid phasein engagement with the outer heat trans er wall at its total pressurewithin the conduit produced in part by the pressure increase from therotating conduit, and yet sufficiently high to provide that the secondfluid is above its boiling point at its partial pressure, excluding thepressure increase from the rotating conduit, within the conduit.

3. A method of transferring thermal energy between first and secondfluids, comprising the steps of providing a fluid conduit for the firstfluid having a fluid inlet and outlet for conducting the first fluidtherethrough and an outer heat transfer wall for separating the firstfluid from the second fluid, rotating the fluid conduit, and conductingthe first fluid through the rotating conduit with its highesttemperature sufficiently low to provide that the first fluid remainssubstantially in its liquid phase in engagement with the outer heattransfer wall at its total pressure within the conduit produced in partby the pressure increase from the rotating conduit, and yet sufficientlyhigh to provide that the first fluid is above the boiling point at itspartial fluid pressure, excluding the pressure increase from therotating conduit, within the fluid conduit.

4. The method of claim 3 wherein the fluid conduit comprises anelongated generally tubular conduit with said outer heat transfer wall,and wherein the first fluid is conducted generally helically through thetubular conduit to increase the scrubbing action and centrifugal forceon the heat transfer wall.

5. in a heat exchanger comprising a fluid conduit with an inlet andoutlet and an outer heat transfer wall for transferring thermal energybetween a first fluid being conducted through the conduit from its inletto its outlet and a second fluid separated from the first fluid by theheat transfer wall, mounting means for mounting the fluid conduit forrotation as the first fluid is being conducted therethrough, andnonrotatable fluid inlet and outlet ducts respectively mounted inassociation with the inlet and outlet of the fluid conduit to conductthe first fluid through the fluid conduit as the conduit rotates, theimprovement wherein the fluid conduit comprises a generally spiral tubeextending at a substantially constant radius from its axis of rotation.

6. The heat exchanger of claim 5 wherein the spiral tube has a generallytwisted form with a plurality of generally spiral convolutions withalternate ridges and grooves.

7. The heat exchanger of claim 5 for transferring thermal energy fromthe second fluid through the outer heat transfer wall to the first fluidfor converting, at least in part, the first fluid from its liquid phaseto its gaseous phase, wherein the heat exchanger comprises motor meansfor rotating the fluid conduit to increase the fluid pressure of thefirst fluid as it is conducted through the fluid conduit to maintain thefirst fluid in substantially its liquid phase in engagement with theouter heat transfer wall.

8. In a heat exchanger comprising a fluid conduit with an inlet andoutlet and an outer heat transfer wall for transferring thennal energybetween a first fluid being conducted through the conduit from its inletto its outlet and a second fluid separated from the first fluid by theheat transfer wall, the improvement wherein the fluid conduit comprisesa generally spiral tube, and wherein the heat exchanger furthercomprises means for mounting the spiral tube for rotation as the firstfluid is being conducted therethrough and with the spiral tube generallysymmetrically about its axis of rotation.

9. The heat exchanger of claim 5 further comprising an enclosure forenclosing at least a portion of the fluid conduit and having anenclosure inlet and an enclosure outlet for conducting the second fluidtherethrough, the enclosure comprising a fluid jacket with jacket inletand outlet ports, and fluid connecting means for connecting one of saidports to one of said ducts to connect the fluid conduit and fluid jacketin series.

2. The method of claim 1 wherein the second fluid is conducted throughthe rotating conduit with its highest temperature sufficiently low toprovide that the second fluid remains substantially in its liquid phasein engagement with the outer heat transfer wall at its total pressurewithin the conduit produced in part by the pressure increase from therotating conduit, and yet sufficiently high to provide that the secondfluid is above its boiling point at its partial pressure, excluding thepressure increase from the rotating conduit, within the conduit.
 3. Amethod of transferring thermal energy between first and second fluids,comprising the steps of providing a fluid conduit for the first fluidhaving a fluid inlet and outlet for conducting the first fluidtherethrough and an outer heat transfer wall for separating the firstfluid from the second fluid, rotating the fluid conduit, and conductingthe first fluid through the rotating conduit with its highesttemperature sufficiently low to provide that the first fluid remainssubstantially in its liquid phase in engagement with the outer heattransfer wall at its total pressure within the conduit produced in partby the pressure increase from the rotating conduit, and yet sufficientlyhigh to provide that the first fluid is above the boiling point at itspartial fluid pressure, excluding the pressure increase from therotating conduit, within the fluid conduit.
 4. The method of claim 3wherein the fluid conduit comprises an elongated generally tubularconduit with said outer heat transfer wall, and wherein the first fluidis conducted generally helically through the tubular conduit to increasethe scrubbing action and centrifugal force on the heat transfer wall. 5.In a heat exchanger comprising a fluid conduit with an inlet and outletand an outer heat transfer wall for transferring thermal energy betweena first fluid being conducted through the conduit from its inlet to itsoutlet and a second fluid separated from the first fluid by the heattransfer wall, mounting means for mounting the fluid conduit forrotation as the first fluid is being conducted therethrough, andnonrotatable fluid inlet and outlet ducts respectively mounted inassociation with the inlet and outlet of the fluid conduit to conductthe first fluid through the fluid conduit as the conduit rotates, theimprovement wherein the fluid conduit comprises a generally spiral tubeextending at a substantially constant radius from its axis of rotation.6. The heat exchanger of claim 5 wherein the spiral tube has a generallytwisted form with a plurality of generally spiral convolutions withalternate ridges and grooves.
 7. The heat exchanger of claim 5 fortransferring thermal energy from the second fluid through the outer heattransfer wall tO the first fluid for converting, at least in part, thefirst fluid from its liquid phase to its gaseous phase, wherein the heatexchanger comprises motor means for rotating the fluid conduit toincrease the fluid pressure of the first fluid as it is conductedthrough the fluid conduit to maintain the first fluid in substantiallyits liquid phase in engagement with the outer heat transfer wall.
 8. Ina heat exchanger comprising a fluid conduit with an inlet and outlet andan outer heat transfer wall for transferring thermal energy between afirst fluid being conducted through the conduit from its inlet to itsoutlet and a second fluid separated from the first fluid by the heattransfer wall, the improvement wherein the fluid conduit comprises agenerally spiral tube, and wherein the heat exchanger further comprisesmeans for mounting the spiral tube for rotation as the first fluid isbeing conducted therethrough and with the spiral tube generallysymmetrically about its axis of rotation.
 9. The heat exchanger of claim5 further comprising an enclosure for enclosing at least a portion ofthe fluid conduit and having an enclosure inlet and an enclosure outletfor conducting the second fluid therethrough, the enclosure comprising afluid jacket with jacket inlet and outlet ports, and fluid connectingmeans for connecting one of said ports to one of said ducts to connectthe fluid conduit and fluid jacket in series.